The following relates generally to wireless communication, and more specifically to multi-level slot format indicator (SFI).
Wireless communications systems are widely deployed to provide various types of communication content such as voice, video, packet data, messaging, broadcast, and so on. These systems may be capable of supporting communication with multiple users by sharing the available system resources (e.g., time, frequency, and power). Examples of such multiple-access systems include fourth generation (4G) systems such as Long Term Evolution (LTE) systems, LTE-Advanced (LTE-A) systems, or LTE-A Pro systems, and fifth generation (5G) systems which may be referred to as New Radio (NR) systems. These systems may employ technologies such as code-division multiple access (CDMA), time-division multiple access (TDMA), frequency-division multiple access (FDMA), orthogonal frequency-division multiple access (OFDMA), or discrete Fourier transform-spread-orthogonal frequency-division multiplexing (DFT-s-OFDM). A wireless multiple-access communications system may include a number of base stations or network access nodes, each simultaneously supporting communication for multiple communication devices, which may be otherwise known as user equipment (UE).
Certain wireless communications systems may support SFI signaling. Generally, the SFI may include a set of bits that indicate a format for one or more slots. The format may include whether an orthogonal frequency-division multiplexing (OFDM) symbol for a slot is configured for uplink, downlink, or unknown communications, e.g., a communication direction for the OFDM symbol. The monitoring period for the SFI (e.g., the time duration or number of slot that the SFI indication covers) is generally configured by the network, for example in a radio resource control (RRC) signal. The UE may monitor the control signal to detect the SFI and then use the indicated slot format for wireless communications during the covered slot(s). While this may be adequate in certain situations, some scenarios may present challenges, such as when the UE is unable detect the SFI indication. For example, the device may not be able to capture the medium and/or the channel may not support the transmission and therefore the device cannot communicate information, e.g., such as transmitting the SFI indication. In this instance, the UE would not know the slot format for the monitoring period.